The present invention relates to a laminate with an atomic layer deposition on an outer surface of a base, in which the atomic layer deposition is produced by an atomic layer deposition method, and a gas barrier film composed of the laminate.
Methods of creating a thin layer film on a substance by using a gas phase, where atoms or molecules of the substance can move like a gas, are generally categorized into Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD).
Two of the major PVD methods are vacuum deposition and sputtering methods. Of these methods, the apparatus for performing the sputtering method is generally higher in cost, but that apparatus produces high-quality thin films with an even film quality and an even film thickness. For that reason, these methods are used widely for display devices such as liquid crystal displays.
For the CVD method, raw material gases are introduced into the vacuum chamber, in which one or more than two kinds of gases are decomposed or reacted on a substrate through application of heat energy. This method may be combined with plasma or catalytic reactions in order to promote the film forming reaction or to decrease the reaction temperature which are necessary when the gases are decomposed or reacted with each other. These methods are called PECVD (Plasma enhanced CVD) and Cat-CVD, respectively. These CVD methods are advantageous in that defects caused in the formed films are few, and can be used in steps for manufacturing semiconductor devices, such as forming gate insulating films.
Meanwhile, in recent years, an atomic layer deposition (ALD method) has raised interest. This ALD method is a technique of forming films, layer by layer, at an atomic level, where substances are adsorbed on a surface to react chemically thereon, and is also classified as a CVD method. However, the ALD method is regarded as being different from the typical CVD method in that a generally used CVD method (i.e., the typical CVD method) uses a single type of gas or a plurality of types of gases together so as to react chemically on the substrate to form a thin film thereon. In contrast, the ALD method is a special film deposition method, where an active gas called a precursor and a reactive gas (this gas is also referred to as a precursor in the ALD method) are used alternately to grow a thin film layer by layer at the atomic level on the substrate, through absorption on the substrate surface and chemical reactions following the absorption.
The ALD method is practically described herein. In this method, an effect, which is known as a “self-limiting effect,” is used, that is when the surface is covered by a certain type of gas during the surface absorption on the substrate, gas absorption will not occur any more. Firstly, the surface absorption is performed during which this effect is used to discharge the remaining non-reactive precursor gas when only one layer of the precursor has been adsorbed. The reactive gas is then introduced to enable the absorbed precursor to be oxidized or reduced so as to obtain only one thin film having a desired composition, following discharging the reactive gas. These processes are provided as one cycle and this cycle is repeated to grow the thin film, thus enabling the film formation. Therefore, with the ALD method, the thin film can be grown two-dimensionally. In addition, this ALD method can provide a thin film with fewer defects, even compared to not only the traditional vacuum deposition and sputtering methods but also the common CVD method.
For this reason, the application of the ALD method is anticipated to be used widely in the packaging sector of food and pharmaceuticals, and the electronic device field.
In addition, there is also a method which is categorized into the ALD method. Though the ALD method includes a step in which the second precursor is degraded and reacted with the first precursor adhered to the substrate, herein the plasma method is used to activate the reaction. This method is called plasma activated ALD (PEALD: Plasma Enhanced ALD) or simply Plasma ALD.
The ALD technique was first proposed by Dr. Tuomo Sumtola of Finland in 1974. Generally the ALD method is able to provide high quality and high density film formation, so the ALD method has therefore been used in the semiconductor field, such as for gate electrode production. This ALD method has also been reported in ITRS (International Technology Roadmap for Semiconductors). Furthermore, compared to other deposition methods, the ALD method has less influence from the oblique shadow effect (which is a phenomenon where sputtering particles enter the surface of the substrate obliquely, causing non-uniformness of the film deposition). Therefore, in the ALD method, the film deposition is possible as long as there is a gap for the gas into the substrate. For this reason, the ALD method is expected to be applied for coating lines and holes of substrates, where the lines and holes have a higher aspect ratio, that is, a higher ratio between the depth and the width, and also to coating three-dimensional structures in MEMS (Micro Electro Mechanical Systems) related systems.
In contrast, demerits of using ALD method are that special materials are necessary and therefore the overall cost is high. In such conditions, the biggest demerit is that it is slower in forming films. For example, compared to the usual vacuum deposition or sputtering method, the film formation speed is 5-10 times slower with the ALD method.
There are a variety of objects in which thin films are formed using the ALD method, they include, small plate-shaped substrates such as wafers and photomasks; larger-area, but non-flexible substrates such as glass plates, or large-area and flexible substrates such as films. There are equipped mass production facilities in which thin films are produced on substrates depending on their applications. In such facilities, various substrate handing techniques have been proposed and put into practical use, from the cost point of view, handling simplicity, and film formation quality, etc.
For mass production apparatuses for thin film deposition on a substrate, there are several types of film deposition apparatuses known. One is a batch type film deposition apparatus, in which a single substrate is supplied as a wafer in a film deposition machine for the film deposition, and then the substrate is replaced by the next substrate for the next film deposition or a plurality of substrates are set at the same time to carry out the same film deposition on the all the wafers.
Another type of the mass production apparatus is exemplified as an inline type film apparatus which forms a film on members such as a glass substrate. In this apparatus, the substrate is conveyed in sequence relative to a source of film formation, during which time film deposition is carried out in parallel with the conveyance. Other types of apparatuses include a coating film formation apparatus which is called a film formation roll to roll coater. In this coater, flexible substrates are un-wound and whilst conveyed the film is formed, and thereafter, wound on to another roll. As the coating film formation apparatus, there can also be provided a web coating film formation apparatus directed to not only for flexible substrates, but also flexible sheets that can continuously convey substrates for film deposition or a partly flexible tray that can convey substrates for continuous film deposition.
For either a film deposition method using the film deposition apparatus and the technique used to process the substrate, deposition apparatuses are combined so as to obtain the ultimate deposition speed, in addition to the consideration of various factors such as the cost, quality and easy processing.
Furthermore, there has been known a technique related to the ALD method (as shown in patent literature 1, for example). This technique discloses deposition of a barrier layer on the surface of a plastic film by performing atomic layer vapor deposition based on the ALD method. In the technique disclosed by the patent literature 1, the atomic layer vapor deposition is performed based on the ALD method so that there can be provided barrier films of higher barrier performance.